Calcium-rich biowastes offer low-cost functional fillers for engineering polymers, but their use in polyamide 6 requires balanced control of interfacial contact, morphology, moisture response, transport behavior, crystallization, and thermal stability. Waste oyster shells were calcined at 1000 degrees C to obtain CaO-rich thermally treated oyster shell powder (TOS), which was incorporated into polyamide 6 by melt blending and compression molding at 5-25 wt%. Comparative characterization against commercial CaO confirmed that TOS contained 98.70 mass% CaO on an oxide-equivalent basis and retained a CaO/Ca(OH)2-rich mineral structure with minor Mg-containing species. The composites showed loading-dependent mechanical, morphological, moisture-related, oxygen-barrier, thermal, and antibacterial responses. The 10 wt% composite gave the best overall balance, increasing tensile strength from 25.0 to 30.5 MPa while maintaining compact fracture morphology, controlled surface roughness, and the lowest moisture content and water absorption. Surface microscopy and elemental mapping confirmed the distribution of Ca-rich domains, whereas excessive TOS caused particle exposure, surface heterogeneity, and local defects. The oxygen transmission coefficient decreased at moderate TOS contents but increased at 25 wt% because of defect-assisted transport. Thermal and crystalline analyses confirmed crystallization regulation and improved early weight-loss resistance. The 10 wt% composite showed antibacterial efficiencies of 95.45% +/- 1.70% against Escherichia coli and 89.41% +/- 1.46% against Staphylococcus aureus. A screening cradle-to-gate assessment estimated a 7.7% material-level reduction in global warming potential, linking waste valorization to verified multifunctional performance.
The organic electric-field regulator enables the polymer to have nonlinear conductivity and to self-regulate electric field. However, it may migrate out from the polymer matrix due to its small molecular weight, causing nonreversible damage to the electrical performance of the composite. In this work, to improve the long-term stability, the allyloxy polyethylene glycol (APEG) with electron-donating groups was grafted onto the low-density polyethylene (LDPE) chains by chemical grafting method. The composites were mainly characterized by weight loss rate, breakdown strength, conductivity, space charge distribution, and surface potential decay. In addition, the quantum chemical calculations were carried out on APEG and grafting APEG/LDPE composites. The results show that grafting APEG on LDPE macromolecules not only improves the long-term stability but also enhances the nonlinear conductivity, which is attributed to the increase in the electrostatic potential of electron-donating groups of APEG. The nonlinear conductivity helps homogenize the electric field distribution in polymer composites and helps dissipate the surface charges. This work lays a foundation for the improvement of all-organic nonlinear dielectrics.
Poly(vinyl alcohol) (PVA) is a commercial polymer with one of the lowest oxygen transmission rates, demonstrating considerable application potential in high-barrier packaging. However, its poor thermal processability severely limits its practical use. Based on molecular complexation technology for thermal processing of PVA developed in our research group, a small amount of boric acid (BA) was further introduced to form both crosslinking and hydrogen bonding in the system while preserving the excellent thermal processability and biaxial stretchability of PVA. In this way, high-performance modified PVA (G-PVA/BA) films were successfully fabricated via melt extrusion and biaxial stretching, leading to a significant enhancement in mechanical properties and barrier performance. With BA addition of only 0.10 wt.%, the biaxially stretched film exhibited an elongation at break of 434% and a tensile strength of 95 MPa, primarily attributing to the notable increase in crystallinity induced by orientation. The well-ordered crystal structure also provided a robust physical barrier, resulting in the low oxygen permeability coefficient of 1.117 & times; 10-18 cm3 & centerdot;cm/(cm2 & centerdot;s & centerdot;Pa) at 23 degrees C and 50% RH. This high-strength, high-barrier PVA film has broad application prospects in fields such as food, tobacco, electronics, and textile packaging.
In this study, waste latex gloves from excess or defective industrial production were recycled and used as a raw material to prepare EVA/waste glove rubber (WGR) composites. WGR was blended with poly(ethylene-co-vinyl acetate) (EVA) at different compositions to investigate how blend composition and maleic anhydride (MAH) grafting affect the chemical, mechanical, and energy-dissipation behavior of the resulting composites. Fourier transform infrared (FTIR) spectroscopy, tensile testing, Shore A hardness measurements, and cyclic compression analyses were conducted to characterize the composites. The results showed that increasing EVA content improved elastic modulus, tensile strength, Shore hardness, absorbed energy, and energy-dissipation capability while preserving substantial elastic recovery under repeated compression. To promote interactions between the EVA and WGR phases and enable effective incorporation of high amounts of WGR, MAH grafting was applied to the EVA/WGR system. The grafted composites exhibited marked improvements in elastic modulus, tensile strength, and generally in elongation at break and absorbed energy compared with ungrafted blends. These improvements were consistent with enhanced interactions and more effective stress transfer between the EVA matrix and WGR particles, and FTIR provided spectroscopic evidence supporting MAH grafting. Among the investigated compositions, the MAH-grafted composite containing 60 phr EVA and 40 phr WGR exhibited the highest first-cycle absorbed energy among the grafted composites under 50% cyclic compression. These findings demonstrate that MAH grafting can facilitate the value-added utilization of waste glove rubber in EVA/WGR composites with enhanced mechanical and cyclic energy-dissipation behavior, suggesting their potential for vibration isolation, shock absorption, and damping-related applications.
Rigid polyurethane foam (RPUF) composites were modified with bio-based chitosan (CS) as a green functional additive to replace conventional synthetic flame retardants for building insulation applications. The RPUF/CS composites were systematically characterized by FTIR, thermogravimetric analysis (TG), limiting oxygen index (LOI), cone calorimetry, smoke toxicity analysis, compression testing, and Abaqus finite element simulation. The optimal formulation with 6 wt% CS (RPUF/CS-6) exhibited the highest initial decomposition temperature, maximum decomposition temperature, char residue, and activation energy among all four heating rates. LOI reached 24.3%, significantly higher than unmodified RPUF. Cone calorimetry at 50 kW/m2 showed that RPUF/CS-6 reduced heat release rate (HRR) by 53.43%, total heat release (THR) by 25.31%, smoke production rate (SPR) by 58.33%, total smoke release (TSR) by 40.38%, and smoke density (Ds) by 23.06%, demonstrating significantly enhanced flame retardancy and smoke suppression performance. Compression tests combined with Abaqus simulation confirmed that CS incorporation substantially enhanced structural integrity and mechanical stability. By replacing synthetic flame retardants with natural polymer CS, this work achieves a unique combination of improved flame retardancy, smoke suppression, and mechanical performance. The experimental and numerical validation provides a robust basis for designing high-performance, low-fire-risk, environmentally friendly RPUF composites. This cleaner production strategy offers a promising route for sustainable building insulation materials.
